Powder Keg was ok. I boarded it in vs Infect, Shardless BUG and Landstill (for Manlands). I have 2 of these instead of 3 Ratchet Bomb because it can hit Manlands. However, Ratchet Bomb and Keg are slow to remove creatures with CMC 2 or higher.

I'm going to switch the Batterskull and the Ensnaring Bridge. Bridge is nice but it doesn't put pressure on the opponent. Duplicant is probably going to be another threat, not sure what yet.

I like the Petals, leaving those in for now. I find a lot of my free wins are the result of having Chalice on 1 turn 1. But I can't go with 4 City of Traitors, I already hate having openers where my only lands are Vesuvas and Cities. I see what you are getting at though. A turn 1 Monolith threatens a Wurmcoil Engine or even a Karn the next turn.